1. Field of the Invention
This invention generally relates to a seat rail system that mounts a vehicle seat thereon. More particularly, this invention relates to a seat rail system with a seat position sensor which detects the position of a car seat mounted thereon in relation to the car floor on which the seat rail system is secured. The positional information of the car seat can be utilized in controlling deployment of an automobile airbag system installed in association therewith.
2. Related Art
Seat belts and airbag systems are standardized equipment of automobiles today. A typical airbag system comprises an impact sensor, gas generating device and airbag with an airbag door.
As is known, indiscriminate full deployment of an airbag, regardless of an occupant's seat position, may be harmful or even dangerous to the occupant if his or her seat position is “too” close to the airbag door.
There has been proposed an airbag deployment adjustment system which detects occupants' seat positions and adjusts deployment of their airbags accordingly. This type of occupant seat position detection can be conventionally provided through utilization of a potentiometer, mechanical limit switch or magnetic field sensor.
A conventional potentiometer system is potentially influenced by change of temperature and may occasionally malfunction or generate inaccurate information. In addition, a conventional potentiometer system may not be very durable due to the abrasive mechanical contact points that the system utilizes. Such mechanical contacts will be worn over time through repeated use and may cause malfunctioning.
A conventional mechanical limit switch system is relatively less reliable as it utilizes relatively less reliable mechanical switching. For improvement of reliability, a mechanical limit switch system requires precision components or use of a hysteresis system so as to offset the inaccuracy of the mechanical elements used. A mechanical limit switch system is relatively less durable due to the abrasive mechanical contact points the system uses which will be worn over time through repeated use and may cause malfunctioning.
A seat rail device 900 utilizing a magnetic sensor system for occupant seat position detection is disclosed in U.S. Pat. No. 6,053,529.
As depicted in perspective and sectional views in FIG. 11 (prior art) attached to this specification, this seat rail device 900 includes a pair of rails 901a and 901b held in vertical engagement, each having a predetermined length. The lower rail 901a is generally U-shaped in section, having flanges which respectively run along the upper edges of the lower rail 901a. The upper rail 901b on which a side portion of a car seat (not shown) is to be mounted is generally rectangular in section. The upper rail 901b has an axial opening underneath with axial steps respectively provided along the two lower edges, where the flanges of the lower rail 901a are engaged in a sliding manner. The rails 901a and 901b can slide relative to each other in their axial directions and change their relative positions.
The lower rail 901a is provided with legs to be secured onto a car floor therewith. The lower rail 901a is also provided on its one side with a U-shaped magnetic sensor device 902 (a combination of a magnet and a magnetic field sensor). The upper rail 901b is provided on its corresponding side with an elongated hooked flange 903 having a length which is shorter than the upper rail 901b. The downwardly extending elongated portion of the hooked flange 903 is received within the U-shaped magnetic sensor device 902 and changes its position relative to the magnetic sensor device 902 as the upper rail 901b moves in its axial directions relative to the lower rail 901a. The relative axial movements of the upper rail 901b and the lower rail 901a affect the measurement of the magnetic field since the hooked flange 903 shields the magnetic field generated by the magnetic sensor device 902. The magnetic change is detected and its information is outputted to be processed by microcomputer. The position data outputted from the microcomputer is used to control airbag deployment of the car airbag system.
This magnetic sensor system may provide accurate and useful position information for utilization in automobile airbag deployment controlling. However, provision of accurate seat position information requires precise relative setting of the magnetic sensor device 902 and the hooked flange 903, considerably elongating manufacturing time and thus pushing up overall manufacturing costs.
Accordingly, it is an object of the present invention to provide a seat rail system which provides reliable car seat position detection.
It is another object of the present invention to provide a seat rail system which can be manufactured at a low cost.
It is another object of the present invention to provide a seat rail system which is not affected by temperature changes.
It is still another object of the present invention to provide a seat rail system which is durable.
Other objects of the present invention will become apparent from the descriptions that follow.